1. Field of the Invention
The present invention relates to a boat propulsion system, and a control device and a control method therefor. More specifically, the present invention relates to a boat propulsion system including an electronically controlled shift mechanism, and a control device and a control method therefor.
2. Description of the Related Art
Conventionally a technique to drive a shift mechanism of an outboard motor using an electric actuator to switch the shift position has been disclosed in, for example, JP-A-2006-264361. In the shift mechanism disclosed in JP-A-2006-264361, the electric actuator engages and disengages a dog clutch to shift gears among forward, reverse, and neutral positions.
It is also known to provide low-speed and high-speed shift positions for each of forward and reverse directions. Specifically, it is known to provide five shift positions, namely low-speed forward, high-speed forward, neutral, low-speed reverse, and high-speed reverse.
A boat is accelerated and in some instances can be decelerated by the shift operations. In some instances, when the boat is to be decelerated or stopped, a gear shift is made to the opposite shift position to the current shift position to generate a propulsive force in the opposite direction to the traveling direction of the boat.
In the case where a gear shift is made to the direction opposite to the traveling direction, however, the rotational direction of a propeller shaft switches to a direction opposite to the direction it was traveling before the gear shift. Thus, a large load is applied to a power source and a power transmission mechanism of the boat at the time of the gear shift to the direction opposite to the traveling direction. In particular, when a gear shift is made to a high-speed forward or high-speed reverse position, a significantly large load is applied to the power source and the power transmission mechanism at the time of the gear shift to the opposite direction to the traveling direction.